Introducing High-Valence Iridium Single Atoms into Bimetal Phosphides toward High-Efficiency Oxygen Evolution and Overall Water Splitting

Single atoms are superior electrocatalysts having high atomic utilization and amazing activity for water oxidation and splitting. Herein, this work reports a thermal reduction method to introduce high-valence iridium (Ir) single atoms into bimetal phosphide (FeNiP) nanoparticles toward high-efficiency oxygen evolution reaction (OER) and overall water splitting. The presence of high-valence single Ir atoms (Ir4+) and their synergistic interaction with Ni3+ species as well as the disproportionation of Ni3+ assisted by Fe collectively contribute to the exceptional OER performance. In specific, at appropriate Ir/Ni and Fe/Ni ratios, the as-prepared Ir-doped FeNiP (Ir-25-Fe16Ni100P64) nanoparticles at a mass loading of only 35 mu g cm(-2) show the overpotential as low as 232 mV at 10 mA cm(-2) and activity as high as 1.86 A mg(-1) at 1.5 V versus RHE for OER in 1.0 m KOH. Computational simulations confirm the vital role of high-valence Ir to weaken the adsorption of OER intermediates, favorable for accelerating OER kinetics. Impressively, a Pt/C||Ir-25-Fe16Ni100P64 two-electrode alkaline electrolyzer affords a current density of 10 mA cm(-2) at a low cell voltage of 1.42 V, along with satisfied stability. An AA battery with a nominal voltage of 1.5 V can drive overall water splitting with obvious bubbles released.

Automated summary

This work presents a thermal reduction method to introduce high-valence iridium (Ir) single atoms into bimetal phosphide (FeNiP) nanoparticles, which exhibit exceptional performance for oxygen evolution reaction (OER) and overall water splitting. The high-valence single Ir atoms (Ir4+) and their synergistic interaction with Ni3+ species, along with the disproportionation of Ni3+ assisted by Fe, contribute to the remarkable OER activity. The Ir-doped FeNiP nanoparticles with appropriate Ir/Ni and Fe/Ni ratios demonstrate low overpotential and high OER activity.